Production and composition of Iberian sow's milk and use of milk nutrients by the suckling Iberian piglet

Abstract

Sixteen purebred Iberian (IB) sows were used in two consecutive trials to determine the efficiency of conversion of sow's milk into piglet body weight (BW) gain and the relationship between milk protein and body protein retention and between milk energy yield and body energy retention in the nursing IB piglet. In each trial, four sows were selected in order to evaluate their milk production, litter growth and nutrient balance measurements, together with four additional sows for milk sampling. Litter size was equalized to six piglets. Daily milk yield (MY) was determined weekly by the weigh-suckle-weigh technique over a 34-day lactation period. Piglets were weighed individually at birth and then weekly from day 5 of lactation. Milk samples were collected on days 5, 12, 19, 26 and 34 post partum. The comparative slaughter procedure was used to determine piglet nutrient and energy retention. One piglet from each litter was slaughtered at birth and four on the morning of day 35. Total MY was on average 5.175 6 0.157 kg/day. The average chemical composition (g/kg) of the milk was 179 6 4 dry matter, 53.4 6 1.0 CP, 58.5 6 3.8 fat, 10.4 6 0.3 ash and 56.9 6 2.3 lactose. Milk gross energy (GE) was 4.626 6 0.145 MJ/kg. Milk intake per piglet tended to increase in trial 2 (832 v. 893 g/day; P 5 0.066). Piglet BW gain contained (g/kg) 172.1 6 1.3 protein, 151.5 6 3.5 fat, 41.4 6 0.6 ash and 635 6 3 water and 10.127 6 0.126 MJ GE/kg. Throughout the 34-day nursing period, the piglets grew at an average rate of 168 6 3 g/day. The ratio of daily piglet BW gain to daily MY was 0.195 6 0.002 g/g and the gain per MJ milk GE intake was 41.9 6 0.5 g/MJ. The overall efficiency of protein accretion (g CP gain/g CP milk intake) was low and declined in trial 2 (0.619 v. 0.571; P 5 0.016). Nutrient and energy deposition between birth and weaning were 27.4 6 0.5 g/day protein, 24.2 6 0.8 g/day fat and 1615 6 40 kJ/day energy. Piglet energy requirements for maintenance were 404 kJ metabolizable energy (ME)/kg BW 0.75 . ME was used for growth with a net efficiency of 0.584. These results suggest that poor efficiency in the use of sow's milk nutrients rather than a shortage in milk nutrient supply might explain the low growth rate of the suckling IB piglet.Keywords: milk production, milk composition, Iberian piglets, protein and energy deposition, nutrient balance ImplicationsThis study suggests that growth rate in the suckling Iberian (IB) piglet is not limited by a shortage in milk nutrient supply but might rather be related to a very low efficiency in the use of milk protein and energy. In the young IB piglet, protein deposition is a costly process, presumably because of a high protein turnover rate, as found in later growth stages. The sharp decrease in milk conversion ratios detected during the last week of the study implies that a lactation period of more than 4 weeks is not to be recommended.

Utilization of milk minerals by Iberian suckling piglets

“…Animals, management and general procedures of the experiment have been described elsewhere (Aguinaga et al, 2011a). Briefly, 16 third-parity purebred IB sows (Silvela strain) were randomly selected from the Montecastilla farm (Granada de Rio Tinto, Huelva, Spain), and used in two consecutive trials (n = 8).…”

“…Milk samples were collected from the four nursing sows on day 5, 12, 19, 26 and 34 postpartum as described in Aguinaga et al (2011a) and stored in opaque plastic bottles at -20ºC until analyzed. This procedure allowed the collection of a great volume of milk (> 100 mL) without disrupting the suckling pattern of piglets involved in the nutrient balance measurements.…”

“…A correction factor was applied to account for piglets' weight losses due to evaporative losses and physical activity during suckling (Klaver et al, 1981). To calculate the total milk intake of each piglet during the 34 days of lactation, it was assumed that milk production changed linearly between the successive measurements (Aguinaga et al, 2011a).…”

“…This is a low performing pig with a low genetic potential for lean tissue deposition (Nieto et al, 2002;Barea et al, 2007;Conde-Aguilera et al, 2011). The slower growth rate of the Iberian suckling piglet, compared with piglets from conventional or lean genotypes, seems to be related to a comparatively decreased efficiency of use of milk energy and protein in the former (Aguinaga et al, 2011a). Nowadays, no available data exist in the literature about the composition of the mineral fraction in IB sow milk.…”

Effects of intermittent suckling on body composition of Iberian piglets weaned at 35 days of age

“…For that purpose, we assumed for the gain to creep feed ratio the value of 0.793 obtained for the BW gain to milk total solid intake ratio by Aguinaga et al (2011a) in Iberian piglets fed exclusively on milk. This ratio of 0.793 was used to estimate the ADG resulting from creep feed consumption during this period, whereas the remaining ADG was assumed to reflect the milk intake of the piglets.…”